Kiyomitsu Asano

Crystallographic Polarity and Etching Behavior of ZnSe

The crystallographic polarity of ZnSe has been identified uniquely by employing X-ray diffraction techniques. The X-ray identification has been correlated with the etch-pit figures formed on the (111)Zn and () Se surfaces. When etched with the K2Cr2O7-H2SO4 solution, the (111) surface is highly polished, while the () surface forms triangular pyramidal shaped pits with positive orientation. Subsequently etched with the NaOH solution, triangular pyramidal shaped pits with negative orientation are formed on the (111) surface, and the positively oriented pits on the () surface formed by the K2Cr2O7-H2SO4 solution develop into negatively oriented pits in triangular pyramidal shape and in addition, triangular pits with flat bottom are formed on the () surface. A similarity in etching behavior has been found between the ZnSe crystals grown from the melt and grown by sublimation techniques.

Microwave Surface Resistance of Bi 2Sr 2CaCu 2Ox Thick Films on Large-Area Metallic Substrates

As a feasibility study for application of a high-T c material to an accelerator cavity, Bi2Sr2CaCu2Ox thick films were formed on large-area metallic substrates. The microwave surface resistance of the films was measured over a temperature range from 4.2 K to 300 K using a demountable cylindrical copper cavity operated at 3 GHz in the TE011 mode. The area of the end plate was 177 cm2 and the thickness of the films was around 50 µm. The films were formed either on silver foils (on copper) or on a silver plate, coated by either a screen-printing or a spray-coating method, sintered either in air or in a Bi2O3 atmosphere, both at 885–890°C, and either annealed in nitrogen gas at 600°C or not annealed. The ratio of the microwave surface resistance of the best film to that of the copper was 0.18 at 10 K and 0.65 at 77.3 K. A comparison of the microwave surface resistance is made between Bi2Sr2CaCu2Ox and YBa2Cu3O7-x films.